VI Classifications of Weldments - publish.illinois.edu
Transcript of VI Classifications of Weldments - publish.illinois.edu
AM 11/03 1
VI Classifications of Weldments
Good Bad
AM 11/03 2
Outline
nn TWI Classification systemTWI Classification systemnn AISC classification systemAISC classification systemnn An alternative classification systemAn alternative classification system
AM 11/03 3
B - Longitudinal butt
AM 11/03 4
C - longit. Butt w/ Reinforcement
AM 11/03 5
C - Transverse Butt, Machined
AM 11/03 6
D - Long. Butt w/ Start-stop
AM 11/03 7
D - Butt weld w/ good toe
AM 11/03 8
E - Butt weld w/ bad toe
AM 11/03 9
F2 - Trans. butt in rolled section
AM 11/03 10
F - Trans. Butt w/ backing strip
AM 11/03 11
F - Attachments on plate face
AM 11/03 12
F - Groove welded cruciform
AM 11/03 13
G - Attachments near edge
AM 11/03 14
F2 - Load carrying fillet weld
AM 11/03 15
W - Fillet weld metal
AM 11/03 16
TWI - Classification system
AM 11/03 17
Application of TWI system
AM 11/03 18
Application of TWI system
AM 11/03 19
TWI rules
AM 11/03 20
Outline
nn TWI Classification systemTWI Classification system
nn AISC classification systemAISC classification systemnn An alternative classification systemAn alternative classification system
AM 11/03 21
10 810 710 610 510 41
10
100
Fatigue Life, N (cycles)
A
B
C
D
E
F
Weld Category
AISC classification system
AM 11/03 22
10 710 610 510 410 310 210 0
10 1
10 2
10 3
run-outsfailures
Fatigue life, N (cycles)
S = 239.55 * N^-0.15296, r = -0.50264, s = 0.13542
logN = 8.1064 - 1.6518*logS, r = -0.45032, s = 0.44503
99% survival with 50% confidence
99% survival with 95% confidence
AISC category B and C
The good welds!
AM 11/03 23
10 710 610 510 410 310 0
10 1
10 2
10 3
failuresrun outs
Fatigue life, N (cycles)
S = 159.20 * N^-0.16648, r^2 = 0.173, s = 0.1718
logN = 6.8974 - 1.03751*logS, r = -0.2387, s = 0.4293
99% survival with 50% confidence
99% survival with 95% confidence
AISC category D and E
The bad welds!
AM 11/03 24
10 710 610 510 410 310 0
10 1
10 2
10 3
A-S99%
B-S99%C-S99%D-S99%
E-S99%F-S99%
Fatigue life, N (cycles)
A
C
B
D
E
F
99% survival with 95% confidence
AISC category best fit lines to data
AM 11/03 25
6.3 A Suggestion for the Classification of Weldments
Good Bad
AM 11/03 26
Ripple
Toe
Root
Termination
Weld stress concentrations
Personal view
AM 11/03 27
4
6
8
10
30
50
70
105 106 107
RippleGroove WeldsNon-Load-Carrying Fillet WeldsLoad-Carrying Fillet WeldsTerminations
Fatig
ue L
ife, N
(cyc
les)
Nominal Stress Range, ∆S (MPa)
Ripple
AM 11/03 28
Groove welded butt joints
4
6
8
10
30
50
70
105 106 107
RippleGroove WeldsNon-Load-Carrying Fillet WeldsLoad-Carrying Fillet WeldsTerminations
Fatig
ue L
ife, N
(cyc
les)
Nominal Stress Range, ∆S (MPa)
AM 11/03 29
Non-load-carrying fillet welds
4
6
8
10
30
50
70
105 106 107
RippleGroove WeldsNon-Load-Carrying Fillet WeldsLoad-Carrying Fillet WeldsTerminations
Fat
igue
Lif
e, N
(cyc
les)
Nominal Stress Range, ∆S (MPa)
AM 11/03 30
Transverse attachments
4
6
8
10
30
50
70
105 106 107
RippleGroove WeldsNon-Load-Carrying Fillet WeldsLoad-Carrying Fillet WeldsTerminations
Fat
igue
Life
, N (c
ycle
s)
Nominal Stress Range, ∆S (MPa)
AM 11/03 31
Longitudinal attachments
4
6
8
10
30
50
70
105 106 107
RippleGroove WeldsNon-Load-Carrying Fillet WeldsLoad-Carrying Fillet WeldsTerminations
Fatig
ue L
ife, N
(cyc
les)
Nominal Stress Range, ∆S (MPa)
AM 11/03 32
40
60
80
100
300
500
105 106 107
RippleGroove WeldsNon-Load-Carrying Fillet WeldsLoad-Carrying Fillet WeldsTerminations
∆S
(MPa
)
Fatigue Life, N (cycles)
Good, bad, maverick
AM 11/03 33
10
100
105
106
107
Fatigue Life, N (cycles)
Nom
inal
Str
ess
Ran
ge, S
(ksi
)
Terminations
Partial Penetration Load-Carrying FilletTermination
RippleNon-Load-Carrying Fillet
Transverse Groove Welded Butt
Good
Bad
Maverick
Nom
inal
Str
ess
Ran
ge, S
(MP
a)
500
50
100
Good welds, Bad welds, Mavericks
AM 11/03 34
C
Detail #3Kf = 1.87
²S design = 27.0 ksi.
C Full-Penetration GrooveWeld: Detail #10
Kf =2.12²S design = 23.3 ksi.
C
Non-Load Carrying FilletWeld: Detail #25
Kf =2.23²S design = 22.1 ksi.
The good welds: weld toe failures
AM 11/03 35
C,CsLoad Carrying Fillet Weld:
Detail #20Kf =3.12
²S design = 17.5 ksi.
C
Weld Termination:Detail #30Kf =3.27
²S design = 14.5 ksi.
The bad welds: terminations
AM 11/03 36
Fatigue severity of terminations
n Starts and stops introduce weld discontinuities.n Residual stresses very high.n 3-D stress concentrations effects.
C
AM 11/03 37
Examples of terminations
C
C
a
b
C
L-PL-P
LP
C
CC
AM 11/03 38
C
P• Partial penetration
weldment. Theamount of penetrationis generally unknown.
C, Cs
C, Cs
• Undercut. Failureoccurs at the undercuton wrap-around weldwhere the arris of theplate is melted. theamount of theundercut is generallyunknown.
The mavericks: something undefined
AM 11/03 39
C
C
• Multiple failure sites.The stress distributionin the joint changes asfatigue cracks initiateand grow at variouslocations.
C
L
P
L-PL-P
• Local stresses uncertainbecause of structuralredundancy
The mavericks: complex components
AM 11/03 40
Summaryn Viewed from the perspective of crack
initiation site, weldments could be grouped into four categories: ripple, toe, root, and terminations.
n This classification scheme leads to the conclusion that there are “Good”and “Bad” weldments and “Mavericks” - weldments for which a critical piece of information is unavailable and hence their behavior is undefined.